1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for dividing a cell into a cell center region and a cell edge region to use a Fractional Frequency Reuse (FFR) scheme in a broadband wireless communication system.
2. Description of the Related Art
In a broadband wireless communication system, a Fractional Frequency Reuse (FFR) scheme may be used to reduce inter-cell interference. In the FFR scheme, a cell is divided into a center region and an edge region, and Mobile Stations (MSs) located in the center region and MSs located in the edge region are set to different frequency reuse rates. For example, if three cells are located as shown in FIG. 1A, each cell uses bands according to the FFR scheme as shown in FIG. 1B. In the case of FIG. 1A, an edge region of a cell A 101, an edge region of a cell B 103, and an edge region of a cell C 105 experience mutual interference. However, a center region of the cell A 101, a center region of the cell B 103, and a center region of the cell C 105 do not experience mutual interference. Therefore, as shown in FIG. 1B, each cell performs communication with MSs located in the edge region through a first band 110 set to a reuse rate of ‘3’ to avoid interference with a neighbor cell, and performs communication with MSs located in the center region through a second band 120 set to a reuse rate of ‘1’. In this case, a band used by each cell in the first band 110 is determined by default.
As described above, when the FFR scheme is used, a Base Station (BS) performs scheduling by identifying the MSs located in the center region and the MSs located in the edge region. Accordingly, the BS has to be able to identify the MSs located in the center region and the MSs located in the edge region. For this, the BS considers a variety of information such as a propagation (or path) loss from a serving cell of each MS, a propagation loss from neighbor cells (or sectors), etc. That is, the use of the FFR scheme results in a large amount of overhead. In particular, when a large number of the MSs are present in a cell, an overhead caused by identification of MSs exponentially increases. Accordingly, when the FFR scheme is intended to be used, there is a need for a method whereby the FFR scheme is correctly performed while minimizing an overhead caused by identification of the MSs.